Hi,
On 16-10-17 01:47, Rafael J. Wysocki wrote:
On Sun, Oct 15, 2017 at 9:24 PM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
Most Bay and Cherry Trail devices use a generic DSDT with all possible
peripheral devices present in the DSDT, with their _STA returning 0x00 or
0x0f based on AML variables which describe what is actually present on
the board.
Since ACPI device objects with a 0x00 status (not present) still get an
entry under /sys/bus/acpi/devices, and those entry had an acpi:PNPID
modalias, userspace would end up loading modules for non present hardware.
This commit fixes this by leaving the modalias empty for non present
devices. This results in 10 modules less being loaded with a generic
distro kernel config on my Cherry Trail test-device (a GPD pocket).
Well, what about hotplug?
On some systems _STA may change from 0 to nonzero for some devices, so
what's going to happen to the modalias then?
A good question. I would expect a change uevent to be generated in
this case and when the device has become present in this new uvent the
modalias will no longer be empty and the module will get loaded, so
the module will not get loaded until the actual hotplug.
The actual generation of this uevent should be done by the various
subsystems based on ACPI_RECONFIG_DEVICE_ADD messages, at which point
adev->status is already updated and then when the subsys calls
acpi_device_uevent_modalias() for the new uevent it will return a
non-empty modalias.
Regards,
Hans
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
drivers/acpi/device_sysfs.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/acpi/device_sysfs.c b/drivers/acpi/device_sysfs.c
index 24418932612e..a041689e5701 100644
--- a/drivers/acpi/device_sysfs.c
+++ b/drivers/acpi/device_sysfs.c
@@ -146,6 +146,10 @@ static int create_pnp_modalias(struct acpi_device *acpi_dev, char *modalias,
int count;
struct acpi_hardware_id *id;
+ /* Avoid unnecessarily loading modules for non present devices. */
+ if (!acpi_device_is_present(acpi_dev))
+ return 0;
+
/*
* Since we skip ACPI_DT_NAMESPACE_HID from the modalias below, 0 should
* be returned if ACPI_DT_NAMESPACE_HID is the only ACPI/PNP ID in the
--
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